Hi There.
I just took a look at your website. You need to change of all the content in giant sized words, for people in a hurry, they want to be able to see quickly what you do or don't do, without reading the whole page, far better to use a list with links straight to the information they want to know, even if the information is just future down the page.
Then underneath these list headings, write all about your business.
Some basic SEO would also help considerably.
Offer some gaurantee for your services, if we don't deliever ontime, you don't pay. testimonals from happy clients.
Consider revising the content on your pages, often the best content is in the last sentence!!!
I link at the bottom of each age to contact you....
As for diversifying, when you make a delivery, and have some spare time, stop and talk to your customers, ask them if their is anything you could offer them, or if they know of anyone that has specific needs.
Especially small businesses, they are more likely to have specific needs, that aren't catered to by large companies.
I know here, the only way to get good delievery rates is to prepay for 100-200 deliveries. Which is a massive outlay for a business that might take 6 to 12 months to use all their delivery tickets. I've heard many a time, that a book of 10 would suit them far better. But for you, 10 delieveries a month, if much better than none.
Drop you business cards off anywhere you can. On you website, ask people to contact you if they have a need you aren't offering offer them a discount for the first time you perform that service.
All the best.